1. Field of the Invention
This invention relates to a method of securing pipes and other long objects against slipping in a fixing device, especially for securing drill pipes or other similar pipes against slipping in slips of the type used in drilling and production of petroleum. The invention also relates to a device for implementing the method.
2. Description of the Prior Art
When retrieving pipe strings during drilling or other similar operations related to petroleum production, the pipe is moved through slips designed to keep the pipe string in a vertical position when screwing stands (sections of piping) on/off the pipe string.
After the pipe string has been raised/lowered by a length corresponding to a length of piping, e.g. by means of the hoisting winch of the drilling device, pipes that are not provided with an external shoulder portion must according to prior art be fitted with a clamp at a position above the slips. The slips is locked, thus gripping the drill string and keeping this in position while the lifting device is disconnected from the pipe string during connection/disconnection of a length of piping.
If the pipe string were to slip in said slips, the clamp is displaced down to a stop against the wedges of the slips. The net weight of the pipe string is transferred via the clamp to the wedges of the slips, thereby causing them to grip the pipe string more tightly. Thus use of a pipe clamp of said type prevents the pipe string from being lost down the borehole.
A new pipe clamp must be fitted prior to removing each stand from the pipe string. The work involved in fitting the pipe clamps causes considerable delay to the pull-up operation.
The pipe clamps must be removed before moving the pipe string back into the well.